To earn this achievement You need to kill 40 wild turkeys in a row while an active timer is counting down. Once you kill a turkey, you will get a 30 second timer. You MUST kill another turkey within the 30 seconds. This will reset back to 30 seconds after every turkey you kill. If the countdown reaches 0, you must start over again.
40 is a lot, and the best place that I have found is in Tirisfal Glades. Not only can you earn the achievement there, but you can also put on pilgrim dress/robe/attire and sit at a seat in Undercity for 1/4 of an achievement. Just watch out for the Horde players that want to prevent you from getting any seat.

Turkinator Achievement
The best place here is to start in Faol's Rest south of the Scarlet Monastary and work your way in a circular path though Venomweb Vale. YOU MUST HAVE YOU MINION ON PASSIVE! No joke, I was at 39 and my voidwalker killed the 40th turkey and I did not get credit for it. I also ran out of time.
To get there take a gryphon flight to Chillwind Point in WPL.
Good luck.

Turkinator Achievement